In glassware manufacture, it is known to provide a glass forehearth the temperature of which is maintained by one or more combustion burners. Operation of the burners may be controlled as a function of feedback obtained from thermocouples disposed in contact with the molten glass in the sidewall channels of one or more zones of the forehearth. Accordingly, detected changes in the temperature of the glass as sensed by the in-glass thermocouples may be used to vary the output of the burners as desired to achieve a desired glass temperature in a given zone of the forehearth. While this may be a generally accurate way to adjust forehearth zone temperatures, the in-glass thermocouples are expensive and require higher capital investments for a given forehearth.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
In one implementation, a system is provided for controlling temperature in a forehearth that includes at least one burner disposed in the forehearth for heating glass in the forehearth, a manifold coupled to the burner, a combustion fuel supply coupled to the burner, a combustion air blower for delivering ambient air under pressure to the manifold, and a controller coupled to the burner for controlling operation of the burner. The system may include a temperature sensor operatively coupled downstream of the blower for providing to the controller a signal indicative of temperature of air delivered to the manifold by the blower. The controller may be responsive to this temperature signal for controlling operation of the burner as a function of current temperature of air fed to the manifold. The controller may also control operation of the burner as a function of an average air temperature over a preceding time duration. In one form, the average air temperature is a moving average air temperature over a predetermined time period.
According to at least one implementation, a method is provided for controlling glass temperature in a forehearth that includes at least one burner associated with the forehearth for heating glass in the forehearth, a manifold coupled to the burner, a combustion fuel supply coupled to the burner, and a combustion air blower for delivering ambient air under pressure to the manifold. The method may include providing to the controller a signal indicative of the combustion air pressure provided to the burner, providing to the controller a signal indicative of the temperature of air downstream of the blower, and controlling the output of the burner as a function of these pressure and temperature signals. In at least one form, the mass flow rate of a combustible air/fuel mixture is maintained constant over varying combustion air temperatures to at least reduce the effect of, for example, changing ambient air temperature.
According to at least one implementation a method is provided for controlling glass temperature in a forehearth that includes at least one burner associated with the forehearth for heating glass in the forehearth, a manifold coupled to the burner, a combustion fuel supply coupled to the burner, a combustion air blower for delivering air under pressure to the manifold, and a cooling air supply communicated with the manifold. The method may include generating a nominal burner pressure curve as a function of the amount of cooling air provided to the manifold wherein the pressure curve includes a first portion in which the temperature downstream of the burner over a first range of desired temperature conditions is controlled at least primarily by adjusting the amount of cooling air provided to the system and the pressure curve includes a second portion in which the temperature downstream of the burner over a second range of desired temperature conditions different from the first range is controlled at least primarily by adjusting the burner pressure. The method may also include controlling the burner pressure as a function of the nominal burner pressure curve. In one form, the burner pressure is controlled as a function of the current air temperature downstream of the blower and also may be controlled as a function of an average air temperature downstream of the blower over a preceding time period.